The present invention relates generally to control systems and more particularly to dynamic inversion control systems.
Dynamic inversion is a method for the design and implementation of control software for realtime, onboard control system computers. A version has been developed by aerospace companies for flight control software for fighter aircraft. Controlling an aircraft's trajectory through the air requires means or effectors (such as the elevator) that can change the aircrafts pitch, yaw, roll, and speed. The main focus of the current versions of dynamic inversion has been control logic for commanding a surplus of means for producing the various forces and moments required. The term surplus implies there are several combinations of effectors, such as thrust vectoring, elevators and canards, that cause the aircraft to pitch, or to yaw, etc. in controllable amounts. Dynamic inversion has been developed to exploit this surplus by 1) increasing the range of total forces and moments beyond the limits of the individual effectors, 2) providing smooth switching to another effector when one reaches its limit, 3) maximizing the potential rate at which forces and moments might be altered, 4) minimizing the impact of a undetected failure in one or more of the effectors, 5) surviving the failure or destruction of some the effectors, 6) varying control laws as the number of free effectors vary with flight mode.
The plant or structure being controlled (e.g. the aircraft and its components) has physical limits that must be observed. For example, the effectors on an aircraft have the power to damage the aircraft's structure (such as tearing off its wings). These physical limits of the plant are not represented in the known dynamic inversion method itself. Thus the known dynamic inversion method may produce outputs that would violate the physical limits of the plant. As a result, these physical limits are enforced via ad hoc logic modifying the inputs to the dynamic inversion method so as to prevent damage to the plant. The ad hoc treatment of the physical limits is not possible where the plant is operating very close to too many physical limits.